Solar Tank

[pixelpixi]

Reading about xinumaster's tank and solar panels (http://www.bareefers.org/discussion/index.php?topic=2609.0 Totally sweet, btw) got me thinking...

It's pretty inefficient to take solar energy, convert it to electricity, and then convert it back to light. Solar panels are at their very best 15% efficient and MH bulbs about 25%. That's a total efficiency of less than 4%.

How about lighting a tank with sunlight directly? I'm thinking a solatube (http://www.solatube.com/) and a light sensor which switches on the tank lights when it's cloudy. I ran the numbers and it appears that given a 4% efficiency of PV+MH, a single 21" diameter "SolaMaster" would move as much energy from the sun to the tank as a 7 foot square PV array.

Has anyone tried something like this?

 

[tuberider]

There's a big thread in the advanced topics forum on RC, I'm sure it'd work.

IME sunlight can lead to browning of some coral, my tank gets a ton of sunlight during the summer, and their is a big difference between summer and winter coloration in my tank.

 

[pixelpixi]

Another data point, according to wikipedia solar radiation on a bright summer day is about 1000 watts/m^2. The 21" solatube is about 1/4 of a square meter, so that's about 250 watts, which is equivalent to a 750 watter MH bulb that's 30% efficient. Not bad!

 

[pixelpixi]

[quote author=tuberider link=topic=4256.msg51182#msg51182 date=1218044279]
There's a big thread in the advanced topics forum on RC, I'm sure it'd work.

IME sunlight can lead to browning of some coral, my tank gets a ton of sunlight during the summer, and their is a big difference between summer and winter coloration in my tank.
[/quote]

Cool. I'll look for that thread. Do you think the problem is too much light, or the color temperature of sunlight being so low? (it's about 6500K) If the latter, maybe a blue gel over the solatube would help.

 

[tuberider]

Yeah I'd imagine it's the CCT, when all that was available was 6500k Iwasakis, most of the Acros I had were brown with blue tips. Even the Stuber stag was brown with blue tips. Fast forward 20 years, and I'll be derned the thing is actually has green coralites and a blue body who'd a thunk.

 

[sfsuphysics]

brown corals, algae loves you, all sorts of great things with sunlight! Of course I was using diffuse sunlight, the other issue is temperature, the light energy itself is enough to warm your tank up quite effectively. I do plan on reintroducing my sunlight frag tank (or secondary tank) as I have a few ideas purring through my head for how to keep temperature on the low.

 

[LeviT]

I've heard of people plumbing their water through the ground to cool it off during the summer but that's another thread

 

[Gomer]

geothermal cooling. There was a recent episode on Dirty Jobs I think of a new retirement community where all their cooling was done this way.

 

[pixelpixi]

[quote author=sfsuphysics link=topic=4256.msg51191#msg51191 date=1218047318]
brown corals, algae loves you, all sorts of great things with sunlight! Of course I was using diffuse sunlight, the other issue is temperature, the light energy itself is enough to warm your tank up quite effectively. I do plan on reintroducing my sunlight frag tank (or secondary tank) as I have a few ideas purring through my head for how to keep temperature on the low.
[/quote]

In theory, temperature should be easier to keep down with with sunlight than with electrical lighting, since with a lamp, 70% of the energy is going directly to heat.

An IR absorbing filter would help too I think. (maybe up in the collector dome)

 

[Gomer]

well..the kicker is that the best cheap IR filter is....water. In theory, you could have a sandwich of water on the input, but then you would want to add something to inhibit growth.

 

[pixelpixi]

[quote author=tuberider link=topic=4256.msg51187#msg51187 date=1218046152]
Yeah I'd imagine it's the CCT, when all that was available was 6500k Iwasakis, most of the Acros I had were brown with blue tips. Even the Stuber stag was brown with blue tips. Fast forward 20 years, and I'll be derned the thing is actually has green coralites and a blue body who'd a thunk.
[/quote]

It seems like that can probably be addressed with a filter too. There are color temperature adjusting gels which are commonly used in for photography that seem like they'd be perfect.

 

[Gomer]

[quote author=pixelpixi link=topic=4256.msg51213#msg51213 date=1218054853]
It seems like that can probably be addressed with a filter too. There are color temperature adjusting gels which are commonly used in for photography that seem like they'd be perfect.
[/quote]

http://www.rosco.com/us/filters/roscolux.asp#Colors

I like the supplied color charts. You can pick your shade and make sure that it doesn't suppress the chlorophyll peaks too much

 

[pixelpixi]

[quote author=Gomer link=topic=4256.msg51212#msg51212 date=1218054571]
well..the kicker is that the best cheap IR filter is....water. In theory, you could have a sandwich of water on the input, but then you would want to add something to inhibit growth.
[/quote]

Haha. That's pretty funny. Any idea what thickness of water would be needed to block a significant percentage of IR?

 

[Gomer]

easy to calculate!

In fact, I am doing that right now for work (just in a different wavelength). one sec while I whip something up.

 

[pixelpixi]

[quote author=Gomer link=topic=4256.msg51216#msg51216 date=1218055474]
[quote author=pixelpixi link=topic=4256.msg51213#msg51213 date=1218054853]
It seems like that can probably be addressed with a filter too. There are color temperature adjusting gels which are commonly used in for photography that seem like they'd be perfect.
[/quote]

Oh they have a "super heat shield" too which looks like it would be perfect for this.

http://www.rosco.com/us/filters/roscolux.asp#Colors

I like the supplied color charts. You can pick your shade and make sure that it doesn't suppress the chlorophyll peaks too much
[/quote]

 

[pixelpixi]

[quote author=Gomer link=topic=4256.msg51218#msg51218 date=1218055660]
easy to calculate!

In fact, I am doing that right now for work (just in a different wavelength). one sec while I whip something up.


[/quote]

I'm sure it's exponential, right? Maybe 85% absorption of IR would be enough?

 

[Gomer]

it is more than just exponential.

Here is a chart for you to look at. bulk water at different thicknesses vs the solar spectrum at noon at the equator.

gas phase water filters out a chunk already, but bulk will filter out more.

 

[LeviT]

:-[ .....uh.... what Tony said

 

[Gomer]

what would be nice to have would be a 1000nm cutoff filter. Time to look into that!

edit: thor has it...now to find out if it is just a coating...

 

[Mr. Ugly]

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